A semifinished eyeglass lens is a lens of which only the convex face is finished (machined) in the process of mass production.
The manufacturer ships this kind of lens to a prescription laboratory which machines the concave face as a function of the requirements of the wearer.
When shipping the lens, it is vital to locate the lens to protect the finished face by preventing it coming into contact with anything, especially in the case of an organic material lens, which scratches very easily.
In the case of a finished lens, on the other hand, both the concave and convex faces are finished in the process of mass production.
The manufacturer ships the lens to the optician, who trims it as a function of the shape of the frame selected by the wearer and morphological parameters specific to the wearer (interpupillary distance, position of the pupils relative to the rims of the frame).
Once again, it is important to protect the faces of the lens because they are finished (i.e. machined and usually carrying treatment layers such as antiabrasion, antireflection and antisoiling layers, for example).